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docs: add complex cross compile worked example

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Andy Green 2017-10-06 09:04:48 +08:00
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READMEs/README.build.md
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@ -409,19 +409,185 @@ you can use as a starting point.
The commandline to configure for cross with this would look like
```
$ cmake .. -DCMAKE_INSTALL_PREFIX:PATH=/usr \
-DCMAKE_TOOLCHAIN_FILE=../cross-arm-linux-gnueabihf.cmake \
-DLWS_WITHOUT_EXTENSIONS=1 -DLWS_WITH_SSL=0
$ cmake .. -DCMAKE_INSTALL_PREFIX:PATH=/usr/lib/my-cross-root \
-DCMAKE_TOOLCHAIN_FILE=../contrib/cross-arm-linux-gnueabihf.cmake \
-DLWS_WITHOUT_EXTENSIONS=1 -DLWS_WITH_SSL=0 \
-DLWS_WITH_ZIP_FOPS=0 -DLWS_WITH_ZLIB=0
```
The example shows how to build with no external cross lib dependencies, you
need to provide the cross libraries otherwise.
**NOTE**: start from an EMPTY build directory if you had a non-cross build in there
before the settings will be cached and your changes ignored.
Delete `build/CMakeCache.txt` at least before trying a new cmake config
to ensure you are really building the options you think you are.
Additional information on cross compilation with CMake:
http://www.vtk.org/Wiki/CMake_Cross_Compiling
@section cross_example Complex Cross compiling example
Here are step by step instructions for cross-building the external projects needed for lws with lwsws + mbedtls as an example.
In the example, my toolchain lives in `/projects/aist-tb/arm-tc` and is named `arm-linux-gnueabihf`. So you will need to adapt those to where your toolchain lives and its name where you see them here.
Likewise I do all this in /tmp but it has no special meaning, you can adapt that to somewhere else.
All "foreign" cross-built binaries are sent into `/tmp/cross` so they cannot be confused for 'native' x86_64 stuff on your host machine in /usr/[local/]....
## Prepare the cmake toolchain file
1) `cd /tmp`
2) `wget -O mytoolchainfile https://raw.githubusercontent.com/warmcat/libwebsockets/master/contrib/cross-arm-linux-gnueabihf.cmake`
3) Edit `/tmp/mytoolchainfile` adapting `CROSS_PATH`, `CMAKE_C_COMPILER` and `CMAKE_CXX_COMPILER` to reflect your toolchain install dir and path to your toolchain C and C++ compilers respectively. For my case:
```
set(CROSS_PATH /projects/aist-tb/arm-tc/)
set(CMAKE_C_COMPILER "${CROSS_PATH}/bin/arm-linux-gnueabihf-gcc")
set(CMAKE_CXX_COMPILER "${CROSS_PATH}/bin/arm-linux-gnueabihf-g++")
```
## 1/4: Building libuv cross:
1) `export PATH=/projects/aist-tb/arm-tc/bin:$PATH` Notice there is a **/bin** on the end of the toolchain path
2) `cd /tmp ; mkdir cross` we will put the cross-built libs in /tmp/cross
3) `git clone https://github.com/libuv/libuv.git` get libuv
4) `cd libuv`
5) `./autogen.sh`
```
+ libtoolize --copy
libtoolize: putting auxiliary files in '.'.
libtoolize: copying file './ltmain.sh'
libtoolize: putting macros in AC_CONFIG_MACRO_DIRS, 'm4'.
libtoolize: copying file 'm4/libtool.m4'
libtoolize: copying file 'm4/ltoptions.m4'
libtoolize: copying file 'm4/ltsugar.m4'
libtoolize: copying file 'm4/ltversion.m4'
libtoolize: copying file 'm4/lt~obsolete.m4'
+ aclocal -I m4
+ autoconf
+ automake --add-missing --copy
configure.ac:38: installing './ar-lib'
configure.ac:25: installing './compile'
configure.ac:22: installing './config.guess'
configure.ac:22: installing './config.sub'
configure.ac:21: installing './install-sh'
configure.ac:21: installing './missing'
Makefile.am: installing './depcomp'
```
If it has problems, you will need to install `automake`, `libtool` etc.
6) `./configure --host=arm-linux-gnueabihf --prefix=/tmp/cross`
7) `make && make install` this will install to `/tmp/cross/...`
8) `file /tmp/cross/lib/libuv.so.1.0.0` Check it's really built for ARM
```
/tmp/cross/lib/libuv.so.1.0.0: ELF 32-bit LSB shared object, ARM, EABI5 version 1 (SYSV), dynamically linked, BuildID[sha1]=cdde0bc945e51db6001a9485349c035baaec2b46, with debug_info, not stripped
```
## 2/4: Building zlib cross
1) `cd /tmp`
2) `git clone https://github.com/madler/zlib.git`
3) `CC=arm-linux-gnueabihf-gcc ./configure --prefix=/tmp/cross`
```
Checking for shared library support...
Building shared library libz.so.1.2.11 with arm-linux-gnueabihf-gcc.
Checking for size_t... Yes.
Checking for off64_t... Yes.
Checking for fseeko... Yes.
Checking for strerror... Yes.
Checking for unistd.h... Yes.
Checking for stdarg.h... Yes.
Checking whether to use vs[n]printf() or s[n]printf()... using vs[n]printf().
Checking for vsnprintf() in stdio.h... Yes.
Checking for return value of vsnprintf()... Yes.
Checking for attribute(visibility) support... Yes.
```
4) `make && make install`
```
arm-linux-gnueabihf-gcc -O3 -D_LARGEFILE64_SOURCE=1 -DHAVE_HIDDEN -I. -c -o example.o test/example.c
...
rm -f /tmp/cross/include/zlib.h /tmp/cross/include/zconf.h
cp zlib.h zconf.h /tmp/cross/include
chmod 644 /tmp/cross/include/zlib.h /tmp/cross/include/zconf.h
```
5) `file /tmp/cross/lib/libz.so.1.2.11` This is just to confirm we built an ARM lib as expected
```
/tmp/cross/lib/libz.so.1.2.11: ELF 32-bit LSB shared object, ARM, EABI5 version 1 (SYSV), dynamically linked, BuildID[sha1]=6f8ffef84389b1417d2fd1da1bd0c90f748f300d, with debug_info, not stripped
```
## 3/4: Building mbedtls cross
1) `cd /tmp`
2) `git clone https://github.com/ARMmbed/mbedtls.git`
3) `cd mbedtls ; mkdir build ; cd build`
3) `cmake .. -DCMAKE_TOOLCHAIN_FILE=/tmp/mytoolchainfile -DCMAKE_INSTALL_PREFIX:PATH=/tmp/cross -DUSE_SHARED_MBEDTLS_LIBRARY=1` mbedtls also uses cmake, so you can simply reuse the toolchain file you used for libwebsockets. That is why you shouldn't put project-specific options in the toolchain file, it should just describe the toolchain.
4) `make && make install`
5) `file /tmp/cross/lib/libmbedcrypto.so.2.6.0`
```
/tmp/cross/lib/libmbedcrypto.so.2.6.0: ELF 32-bit LSB shared object, ARM, EABI5 version 1 (SYSV), dynamically linked, BuildID[sha1]=bcca195e78bd4fd2fb37f36ab7d72d477d609d87, with debug_info, not stripped
```
## 4/4: Building libwebsockets with everything
1) `cd /tmp`
2) `git clone ssh://git@github.com/warmcat/libwebsockets`
3) `cd libwebsockets ; mkdir build ; cd build`
4) (this is all one line on the commandline)
```
cmake .. -DCMAKE_TOOLCHAIN_FILE=/tmp/mytoolchainfile \
-DCMAKE_INSTALL_PREFIX:PATH=/tmp/cross \
-DLWS_WITH_LWSWS=1 \
-DLWS_WITH_MBEDTLS=1 \
-DLWS_MBEDTLS_LIBRARIES="/tmp/cross/lib/libmbedcrypto.so;/tmp/cross/lib/libmbedtls.so;/tmp/cross/lib/libmbedx509.so" \
-DLWS_MBEDTLS_INCLUDE_DIRS=/tmp/cross/include \
-DLWS_LIBUV_LIBRARIES=/tmp/cross/lib/libuv.so \
-DLWS_LIBUV_INCLUDE_DIRS=/tmp/cross/include \
-DLWS_ZLIB_LIBRARIES=/tmp/cross/lib/libz.so \
-DLWS_ZLIB_INCLUDE_DIRS=/tmp/cross/include
```
3) `make && make install`
4) `file /tmp/cross/lib/libwebsockets.so.11`
```
/tmp/cross/lib/libwebsockets.so.11: ELF 32-bit LSB shared object, ARM, EABI5 version 1 (SYSV), dynamically linked, BuildID[sha1]=81e59c6534f8e9629a9fc9065c6e955ce96ca690, with debug_info, not stripped
```
5) `arm-linux-gnueabihf-objdump -p /tmp/cross/lib/libwebsockets.so.11 | grep NEEDED` Confirm that the lws library was linked against everything we expect (libm / libc are provided by your toolchain)
```
NEEDED libz.so.1
NEEDED libmbedcrypto.so.0
NEEDED libmbedtls.so.10
NEEDED libmbedx509.so.0
NEEDED libuv.so.1
NEEDED libm.so.6
NEEDED libc.so.6
```
You will also find the lws test apps in `/tmp/cross/bin`... to run lws on the target you will need to copy the related things from /tmp/cross... all the .so from /tmp/cross/lib and anything from /tmp/cross/bin you want.
@section mem Memory efficiency
Embedded server-only configuration without extensions (ie, no compression